Variable-capacity rotary pumps



Nov. 27, 1962 G. "r. SHOOSMITH 3,065,706

VARIABLE-CAPACITY ROTARY PUMPS 3 Sheets-Sheet 1 Filed March 17, 1961 J4 2g 26 Z4 J2 20) E] i 9 0 4/ l2 I: I 42- c: In

' lnvenlqr Filed March 1'7. 1961 Nov. 27, 1962 G. -r. SHOOSMITH 3,065,706

VARIABLE-CAPACITY ROTARY PUMPS 3 Sheets-Sheet 3 Inventor I 5 917 iwo-owwwt.

y bwadr-Qgfl v 3,65,7d6 Patented Nov. 2?, 1952 3,065,706 VARIABLE-CAPACITY ROTARY PUMPS Guy Taite Shoosmith, St. Mary Bourne, England, assignor to Plenty and Son Limited, Newbury, England Filed Mar. 17, 1961, Ser. No. 96,599 Claims priority, application Great Britain Mar. 18, 1960 2 Claims. (Cl. 103120) This invention relates to variable-capacity rotary pumps, particularly pumps of the sliding vane type.

In a number of prior British Patentsfor example, Patent No. 689,313we have described variable-capacity rotary pumps which comprise a pump casing containing a rotor shaft provided with slots which receive a number of sliding vanes. The outer ends of these sliding vanes bear on fiat surfaces formed internally on a rotor which surrounds the shaft, and the rotor is supported for rotation in a block mounted for limited sliding movement within the pump casing. Movement of the block causes the axis of the rotor to be displaced relatively to the axis of the shaft, with the result that the capacity of the pump is varied.

The present invention is particularly applicable to pumps of the above-mentioned construction, and has as its aim the provision of means which ensure that liquid being passed through the pump cannot leak into the spaces above and below the sliding block.

According to the invention, a variable-capacity rotary pump comprises a rotor carried by a block which is arranged for sliding movement within the pump casing so that the capacity of the pump can be varied, in which one or more liquid-tight seals are provided between mating surfaces on the sliding block and the pump casing so that the spaces at either end or on opposite sides of the sliding block are sealed off from the interior of the block.

The invention is particularly advantageous when it is incorporated into a pump which is intended to handle very viscous liquids such as bitumen or cream. Were such liquids to leak from the pumping chamber into the spaces flanking the sliding block, the sliding block would become very difiicult to move for the purpose of varying the capacity of the pump. Another beneficial application of the invention is to pumps for handling foodstufis which are liable to go bad. In such cases it is important to prevent the egress of foodstuffs from the interior of the sliding block, and the present invention provides a pump which meets this requirement.

In order that the invention may be thoroughly understood, three different pumps in accordance with it will now be described, by way of example, with reference to the accompanying drawings, in which:

FIGURE 1 is a vertical section through one form of p p;

FIGURE 2 is a horizontal section through the same p p;

FIGURE 3 is a perspective view of part of the pump shown in FIGURES 1 and 2;

FIGURE 4 is a perspective view illustrating a modification to the pump shown in FIGURES 1-3;

FIGURE 5 is a section through a detail of the pump component shown in FIGURE 4;

FIGURE 6 is a vertical section through another form of pump;

FIGURE 7 is a horizontal section through the pump shown in FIGURE 6; and

FIGURE 8 is a perspective view of part of the pump shown in FIGURES 6 and 7.

The pump shown in FIGURES 13 is a variable-capacity rotary pump of the sliding vane type which comprises a pump casing 143 containing a rotor shaft 12 provided with slots which receive a number of sliding vanes 14. The outer ends of these sliding vanes bear on flat surfaces 16 formed internally on a rotor 18 which surrounds the shaft, and the rotor 18 is supported for rotation in a block it) mounted for limited sliding movement in a vertical direction within the pump casing 10. Movement of the block 2i) as a result of rotation of the control wheel 21 causes the axis of the rotor 13 to be displaced relatively to the axis of the shaft 12, with the result that the capacity of the pump is varied. Liquid enters the pump through the suction passage 22 and leaves it through the delivery passage 2 the sliding block being provided with an inlet opening 26 and a delivery opening 28 to allow this through-flow of liquid.

It has been found that, in certain circumstances, it is important to prevent liquid which is passing through the interior of the sliding block 24 from leaking into the spaces 3d and 32 lying above and below it. Accordingly, the flat surface on each of the four vertical sides of the sliding block has an annular recess 34, 36, 38, 40 which receives a rubber O-ring 42 arranged to make sealing contact with the flat mating surface of the pump casing. The annular recesses 38 and 42 in two opposite sides of the sliding block are so formed as to surround openings 44 in those sides which receive the rotor 18 and the rotor shaft 12, while the annular recesses 34 and 36 in the other two sides of the sliding block surround the inlet and outlet openings 26 and 28 of the block. If desired, the four annular recesses 34, 36, 38, 40 can be formed in the inner surfaces of the pump casing It) instead of in the sides of the sliding block 20.

A modification to the sliding block of the pump shown in FIGURES l3 is illustrated in FIGURES 4 and 5. The main diiference between the two blocks is that the block 2% shown in FIGURE 4 has two concentricallyarranged annular recesses and O-rings in each side wall instead of only one such recess. The two annular recesses 36, 3'7 and 38, 39 on each side wall of the sliding block are preferably spaced about 1 inch apart, and the thin annular space 46 (see FIGURE 5) formed between the O-rings located in the recesses is filled with grease which is forced through passageways 43 in the pump casing. This arrangement not only ensures that liquid passing through the interior of the block cannot leak into the spaces 3%) and 32 above and below the sliding block, but also allows those spaces to be supplied with hydraulic liquid for the purpose of varying the position of the sliding block within the pump casing without there being any risk of the two liquids contaminating each other.

The pump shown in FIGURES 6-8 is similar to that shown in FIGURES 13, but in this case the possibility of leakage from the interior of the sliding block 20 is reduced still further by making the inlet and outlet passages of the pump integral with the sliding block. The sliding block 20 is therefore provided with two hollow arms 50 and 52 which project through openings 54 and 56 in two opposite sides of the pump casing 10. This construction makes it unnecessary to provide O-rings in the sliding block surrounding the inlet and outlet passages, but O-rings 42'surrounding the rotor 18 and the rotor shaft 12 are provided in the same way as in the pump shown in FIGURES 1-3. The outwardlyextending hollow arms 50 and 52 forming part of the sliding block 26 thus move up and down with the main body of the sliding block during adjustment of the capacity of the pump, and the connecting pipes 58 and 6!) attached to the outer ends of the hollow arms must therefore be sufliciently flexible to allow such movement of the arms to take place.

Although the invention has been described above in connection with a certain construction of pump, it is not restricted to that form of pump. It is, in fact, applicable generally to those variable-capacity rotary pumps which have a rotor carried by a block arranged 3 for sliding or other movement, and which have spaces above and below or an opposite sides of the movable block.

I claim:

1. A variable-capacity rotary pump comprising a hollow pump casing, a suction passage and a delivery passage in said pump casing, a hollow four-sided sliding block slidably mounted within said pump casing, a rotor rotatable within said pump casing, shaft means to rotate said rotor means mechanically connected to said sliding block and arranged externally of said pump casing on an upper portion thereof for slidably moving said sliding block to alter the relative positions of said sliding block and said rotor shaft, a pair of closed chambers flanking said sliding block within said pump casing, each of said closed chambers being bounded on one side by the outer surfaces of said sliding block and the inner surface portions of the pump casing, portions of said pump casing and said sliding block having flat mating surfaces on four sides of said Sliding block cooperatively arranged to reduce to sliding clearances only any communication between said closed chambers and said suction passage, said delivery passage and the interior of said hollow sliding block, a first pair of liquid-tight sealing rings located between said mating surfaces and surrounding a liquid inlet opening and a liquid delivery opening on two opposite sides of said four sides of said sliding block, and a second pair of liquid-tight sealing rings located between said mating surfaces and surrounding openings in the remaining two sides of said four sides of said sliding block, said lastmentioned openings receiving said rotor shaft, a second sealing ring concentrically surrounding each one of said sealing rings provided on said four sides of said sealing block, and grease-passageways being provided in said pump casing whereby annular clearance spaces formed between adjacently-arranged concentric sealings rings may be filled with grease.

2. A variable-capacity rotary pump comprising a hollow four-sided pump casing, a pair of openings in two opposite sides of said pump casing, a hollow foursided sliding block having openings in the four sides thereof slidably mounted within said pump casing, a pair of hollow arms extending from two of said openings in opposite sides of said sliding block through said openings in said pump casing and communicating with the interior of said sliding block to form a liquid inlet passage and a liquid delivery passage respectively, a rotor rotatable within said pump casing, shaft means to rotate said rotor projecting through the remaining two of said openings in the sliding block, means mechanically connected to said sliding block and arranged externally of said pump casing on an upper portion thereof for slidably moving said sliding block to alter the relative positions of said sliding block and said rotor shaft, a pair of closed chambers flanking said sliding block within said pump casing, each of said closed chambers being bounded on one side by the outer surfaces of said sliding block and the inner surface portions of the pump casing portions of said pump casing and said sliding block having flat mating surfaces on four sides of said sliding block cooperatively arranged to reduce to sliding clearance only any communication between said closed chambers and said sliding block interior, and a pair of liquid-tight sealing rings located between said mating surfaces and surrounding said second pair of openings of said sliding block.

References Cited in the file of this patent UNITED STATES PATENTS 1,400,282 Gates Dec. 13, 1921 2,159,941 Guinness May 23, 1939 2,287,369 Anderson June 23, 1942 2,895,423 Shoosmith July 21, 1959 2,908,177 Powell Oct. 13, 1959 FOREIGN PATENTS 689,313 Great Britain Mar. 25, 1953 

